Telephone system



Oct 22, 1940- H. P. MAHoNEY ET A1. 2,218,351

TELEPHONE SYSTEM Filed May 4, 195s 4 sheets-sheet 1 lllllw .36

a, Y ATroRNEY5.

Oct; 22, 1940.

H. P. MAHoNl-:Y g1' A).

TELEPHONE SYSTEM Filed May 4, 1938 Sheets-Sheet 2 BY l CLARENCE LLOMAX ATTORNEY 5.

l Oct 22, 1940- H. P. MAHONEY ET A1. 2,218,851

TELEPHONE SYSTEM 4 Sheets-Sheet 3 Filed May l4, 195s 5. w x n www m VN mom m H AE. `MM Rm YE RR AL HCM. V.. B M .07...

06t- 22, 1i940- H. P. MAHONEY ET AL 2,218,851

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e 5 R Y O X E mYA m EMM O L Wmo m AE. ME am YE RR RA AL HC mwlvu Nmvu Patented Oei. 22, 1940 PATENT voi-Ficia TELEPHONE SYSTEM Harry Mahoney and Clarence Lomax, Oak Park, IIL, assignors to Associated Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application May 4, 193s, serial No. zoaoos 30 Claims.

'Ihe present'inventlon relates to improvements in telephone systems and has for one of its objects the provision of improved apparatus for terminating multi-party subscribers lines in a 5 telephone exchange which utilizes automatic switching equipment for setting up connections between the various lines of the system.

In the usual arrangement of existing installed automatic exchanges, wherein certain of the lines l extending to the exchange are of the rural multiparty type and others are of the single party type, no differentiation is made between the lines as regards the method of terminating the lines in 'i the automatic switching equipment. As a result, l the initiation of a reverting call on one of the rural lines usually results in the seizure of certain of the regular automatic switching equipment provided in the terminating exchange More particularly, when a reverting call is initiated on a multi-party line, one of the non-numerical I automatic switches provided in the exchange is assigned to the use of the line having the calling condition thereon and operates to switch the calling line through to one of the numerical im- 95 pulse responsive switches. In certain instances,

the seized switches are held operated for the duration of the reverting call. paratus is provided for causing the release of the operated switches after a predetermined time interval haselapsed following the seizure of the switches. In either case, certain of the regular automatic switching equipment is tied up so that it can not be .used by the other lines.

In applicants copending application Serial No. 196,136, filed March 16, 1938, there is disclosed an improved arrangement for preventing any of the regular automatic switching equipment of the automatic exchange from being taken for use or hold out of service when the multi-party lines extending to the exchange areoccupied with reverting calls. In brief, the apparatus provided for this purpose comprises a plurality of test links or repeaters at which the multi-party lines terminate and common equipment including an allotter or link distributor for assigning individual ones of the links to the use of successivecalling ones of the multi-party lines. Each test link has embodied therein an impulse responsive In other systems, ap-

calls routed by way of the automatic switching equipment tothe multi-party lines, the selective signaling of the substations on the called lines is accomplished by utilizing code ringing and, more particularly, by equipping the connector sm'tches having access to the lines with impulse responsive to the lines must be equipped for selective codey ringing. f

It is a further obje^t of the present invention,

therefore, to provide, in an automatic telephone system including multi-party subscribers lines, improved apparatus individual to the multi-party subscribers lines for preventing any of the regular automatic switching equipment from being taken for use by aline having access to the equipment when a reverting call is initiated thereon.

It is an additional object to provide in -improved multi-party line terminating equipment of the character described, apparatus `for automatically projecting ringing current over the associated line in response to the seizure thereof by one of the numerical switches, thereby to eliminate this function from the numerical switch or switches having access thereto.

It is a still further object of the invention to provide, in association with a line of the multiparty type and terminating in automatic switching equipment, an improved arrangement for `maintaining the line marked as busy when it is occupied with a reverting call.

More particularly, it is an object of the invention to provide, in association'with a line of the multi-party type and terminating in automatic switching equipment, improved line-busying apparatuswhich operates when a call is initiated on the associated-line, which functions to maintain the line marked as .busy independentlyy of its idle or busy'condition, and which functions to test the line at spaced intervals and to remove the busy marking when a test indicates that the line is idle.

It is another object of the invention to provide, in association with a subscribers line of the multi-party type and terminating in the automatic switching equipment in an automatic exchange, improved apparatus so arranged that certain of the substations associated with the line may be equipped for full automatic service and others of the substations may be equipped for manual service only.

Two embodiments of the invention are illustrated and described in detail hereinafter. In each embodiment, the multi-party lines are of the ground return type and each thereof extends between an automatic exchange and a manual oilice. At the manual olilce, the lines individually .M terminate in the apparatus provided at a manual voperators telephone station, whereas, in the automatic exchange, the lines are individually terminated at a group of numerical switches by way of which connections are routed from the single party lines of the system to the multi-party lines. Also, in the automatic exchange, the multi-party lines are individually terminated in test linksror repeaters which are operative to render the regular automatic switching equipment provided in the exchange accessible thereto. More particularly, each multi-party line extends to a test link or repeater which is connected by way of a trunk line to a non-numerical switch located in the exchange. Individually provided at the respective substations associated with the respective multiparty'lines are manually operable magneto generators which are used for signaling between the substations of the lines on reverting calls. In each of the embodiments of the invention there is provided, in each of the test links or repeaters, an automatic switch which responds to a predetermined series of impulses transmitted by Way of the associated line, or, in other words, to a predetermined operation of the impulsing device provided at the calling substation associated with the calling line, to switch. the line through to an associated one of the non-numerical switches. Also, in each embodiment of the invention, the arrangement of the apparatus is such that a call initiated on one of the single party lines and intended for a substation on one of the multiparty lines may be extended through a portion of the automatic switching equipment provided in the automatic exchange and routed over the called multi-party line to the operators telephone station in the distant manual office. 'I'hrough the intervention of the operator, the desired substation on the called line may be signaled by projecting ringing current from the generator provided at this station back over the called line to the ringing device at the desired substation. Also, in each embodiment of the invention, a call initiated at one of the .substations on a multi-party line and intended for a substation on one of the single party lines terminating at the automatic exchange may be routed over the calling multi-party line to the operators station in the distant manual ofce and then routed from this station back over the multiparty line and through a portion of the automatic switching equipment to the line desired by the calling party. In one embodiment of the invention, it is further contemplated that reverting calls shall be completed only through the intervention of the operator in the manual office, .a call first being routed to the operators telephone station, after which the desired substation on the calling line is signaled from this station by projecting ringing current back over the calling line to the desired called substation. In theother embodiment of the invention, it is contemplated that reverting calls initiated on-the multi-party lines shall be completed without the intervention of an operator, suitable provisions being made in the test links or repeaters individually terminating the multi-party lines for marking the lines as busy when occupied with revertingcalls. More particularly, in this modied arrangement, each. ofthe test links is provided with line vbusying apparatus which operates in response to the initiation of a call on the line and which functions to maintain the associated line marked as busy in the numerical switches to which it extends independently of its idle or busy condition. This apparatus functions automatically to test the associated line to determine its idle or busy condition, 'to maintain the line marked as busy so long as a busy condition prevails, and to remove the busy marking when a test indicates that the line is idle.

As indicated above, code ringing is utilized for selectively signaling the substations on the multiparty lines. In one' modification of the system, such code ringing is under the control of the operator in the manual ofdce. In the second modification of the system, however, it is contemplated that the intervention of the operator on calls to be extended to the substations on the multiparty lines shall not be required, each of the test links or repeaters being equipped with an impulse responsive code selecting switch which is arranged to respond to a code selecting digit dialed at any calling substation and functions to select the particular code corresponding to the desired called substation on the selected called line. The provision of these co'de selecting switches in the repeaters `eliminates the necessity' of providing connector switches with special code selecting apparatus. y v

Further features of the invention pertain to the particular arrangement of the circuit elements whereby the above-outlined objects of the invention are realized.

The novel features believed to be characteristic of the invention are set forth with particularity in the appended claims.l The invention, both as to its organization and method. of operation, together with further objects and advantages thereof, will best be understood by reference to the specification taken in connection with the accompanylng drawings in whichFigures 1 and 2 illustrate one embodiment of an automatic tele-v phone system having incorporated therein certain features of the invention as briefly outlined above, and Figs. 3 and .4 illustrate a modified system arrangement having incorporated therein additional features of the invention as outlined above.` Y

Referring now to Figs. 1 and 2 voi' the drawings, the telephone system there illustrated comprises an automatic exchange, as shown in Fig. 1 and the right portion of Fig. 2; a manual oillce 20| illustrated in Fig. 2; atplurality of single party lines, one of which is illustrated at IDI, extending to the automatic exchange; a multi-party rural line 245 of the ground return type extending between the manual olce and the automatic exchange; an operators telephone station in the manual oiilce; and a` plurality of subscribercontrolled automatic switches including the line switcheslll and H5, two selector' switches HIB and |20, and two connector switches IIII and |25, for setting up connections between the various subscribers lines. Although a single multiparty rural line-245 is shown, it will be understood that additional lines of this character, and having associated therewith equipment identical in form with that illustrated, may be provided. .'I'he equipment associated with the line 245 comprises a test link or repeater which is illustrated in detail in the right portion of Fig. 2 and in Fig. 1 and is described in detail hereinafter. Associated with the line 245 are a plurality of substations of the local battery type, twoy of transmitter and receiver, a cradle or hook switch, a ringer, and an impulsing device for transmitting the switch control impulses by way of the associated line to the automatic switching equipment located in the terminating exchange.

The modified arrangement illustrated in Figs. 3 and 4 is, in general, substantially the same as that illustrated in Figs. 1 and 2. In brief, the system illustrated in Figs. 3 and 4 comprises an automatic exchange; a manual oiiice 480; a plurality of lsingle party-subscribers lines, one of which is indicated at 30| extending to the automatic exchange; a multi-party rural line 436 of the ground return type extending between the manual office 480 and the automatic exchange; and a plurality of subscriber-controlled automatic switches, including two line switches 300 and 400, two selector switches 305 and 405, and two connector switches 3|0 and 4|0, for setting up connections between the various lines of -the system. The end of each single partyy subscribers line remote from the automatic exchange terminates in a substation equipped for full automatic service, that associated with the line 30| being diagrammatically illustrated at E and comprising substation equipment which may be identical with that provided at the substation C, for example. The multi-party line 48'6 terminates in a repeater comprising the circuit elements illustrated in detail in Figs. 3 and 4. Associated with this line are a plurality of substations, certain of which are equipped for full automatic service and others of which are arranged for manual service only. More particularly, with the system illustrated, the substation A' is equipped for manual service, the arrangement being such that only reverting calls, or calls to the manual oiiice 480, may be successfully .completed without the intervention of an operator in the manual ofce. The substation B', on the other hand, is equipped for full automatic service, the equipment provided at this substation including, in addition to the usual magneto generator, ringer, and telephone hand set, an impulsing device so arranged that calls to the automatic subscribers lines may be completed in the usual manner and without the intervention of an operator in the exchange 480, by dialing the regular directory number of the desired automatic subscribers line or substation. i

It is pointed out generally with reference to each of the two modifications briefly described above that the line switches |00, ||5, 300 and 400 lecting functions other than that 'of automatically selecting idle `ones of the selector switches. The `selector and connector switches, on the other hand, are commonly known as numerical switches in that they are individually operative to perform line selecting functions in response to impulses' transmitted thereto. It will be understood that, in each of the two systems illustrated, a plurality of switches of each type, namely, a plurality of line switches, a plurality of selector switches, and a plurality of connector switches, are provided in the system for performing the usual line switching functions. The numerical switches of each type are respectively arranged in groups and, in accordance with universally. vfollowed practice, the number of switches in each group is determined by the maximum volume of tramo the particular switch group is requiredto handle. Further in accordance with conventional practice, each of the single party subscribers lines is multipled to the corresponding bank contacts of a group of connector switches, whereby a plurality of switches are available for setting up connections between each line and any other line of the system. The line switches, on the other hand, are individually associated with the respective subscribers lines, that terminating the line |0| being indicated at |00 and that terminating the line being indicated at 300.

Each of the line switches |00, |-|5, 300, 400, etc., is preferably of the well-known rotary type, of which there are several commercial embodiments. switches, on the other` hand, is preferably of the well-known Strowger type having embodied therein av Strowger switching mechanism including a plurality of bank contacts arranged in levels; a wiper carriage structure adapted to be translated vertically to bring the wipers thereof to a position opposite a particular level of bank contacts and then rotated to bring the wipers into engagement with a particular set of contacts in a selected level; vertical, rotary, and release magnets; and relays suitably connected and arranged to control the energization of the various magnets and the line switching in accordance with the particular functions of the particular switch. Obviously, the particular arrangement of the control apparatus embodied in theswitches of different type is different in each instance vdepending upon the character of the switch.`

Neglecting for thev present the details of the Vapparatus terminating the multi-party subscribers lines and considering generally the operation of the`syStem illustrated in Figs. 1 and 2, for example, when a subscriber, such, for example, as the subscriber at the telephone station C, initiates a call over the line|0| to a second automatic subscribers telephone by lifting his receiver from its hook, a loop circuit is completed by way of the line |0| for initiating the operation of the line switch |00 to select a trunk line leading to an idle selector switch. Assuming, for example, that the selector switch los is the mst numeni switch selected by the line switch |00 for the use of the calling line |0|, when the trunk line leading to this selector switch is found, the loop circuit is extended thereto and the'selector switch is conditioned to respond to the ilrst series of impulses dialed at the calling substation. With the selec- Each of the selector and connector tor switch in this condition, dial tone is returned over the established loop to the calling subscriber to indicate that the dialing operation may be started. When the first digit is dialed at the calling substation, the switch |05 elevates its wipers to a position opposite the level of bank contacts terminating the trunk lines respectively extending to the connector switches having access to the called line. Following this operation, the wipers of the switch |05 are automatically stepped over the contacts of the selected level until the trunk line leading to an idle connector switch of the selected group is found. Assuming, for example, that the connector switch ||0 is the first idle connector switch available, when the Wipers of the switch `|05 are stepped into engagement with the contacts terminating the trunk line extending to this connector switch, the subscribers loop circuit is extended thereto, thereby to cause the connector switch ||0 to be conditioned 'to respond to the second and third series of impulses dialed at the calling substation. In response to the dialing of the second digit, the wipers of the connector switch ||0 are stepped vertically to a position opposite the level of bank 'contacts at which are terminated the lines of the ten-line subgroup including the called line. Following this series of impulses, the connector switch'is conditioned to rotate its wipers step by step in accordance with the impulses making up the third and nal digit dialed at the calling substation. When this final digit is dialed, the wipers of the switch ||0 are stepped into engagement with the set of bank contacts terminating the called line. In accordance with conventional practice, suitable provisions are made in the connector switch ||0 for testing the called line to determine its idle or busy condition, for returning busy tone over the established loop to the calling subscriber in case the called line is busy, and for applying ringing current to the called line in the event this line is idle at the time it is selected. Assuming the called line is idle, the desired conversational connection is completed when the call is answered at the called substation. Also, in accordance with conventional practice, the apparatus is arranged to insure its release when the connection is cleared out at the calling `and called substations. To this end, the control apparatus embodied in the connector switch ||0 is so arranged that the release of the connection is entirely under the contrcl of the calling party.

The mode of operation of the automatic switching equipment diagrammatically illustrated in Figs. 3 and 4 to establish a connection'between .two single party automatic subscribers lines is substantially identical with that just described with reference to the apparatus illustrated in Fig. 1. For thisreason, and inthe interests of brevity, it is deemed unnecessary to comment generally on the operation of the apparatus illustrated in.Figs. 3 and 4.

Referring now more particularly to the apparaus provided in association with the multi-party line 2,45, and considering first the repeater or test link as illustrated in Figs. l and2, this repeater comprises a repeating coil |30, a line or impulse responsive' relay Ri 50, a slow-to-release hold relay R|.40, and a switching-through relay R|30 which is under the control of y an impulse responsive switch |10. The repeater terminates one end of a trunk line |35 which extends to the non-numerical line switch ||5 and to the bank contacts of the connector switches in the group including the switch Il. The switch |10 is preferably ,of the well-known minor type and comprises a single set of bank contacts I'H, a wiper |12, an operating magnet |13 for driving the wiper i12 over the contacts of the set Hi, s release magnet |14, and off-normal springs |15 for controlling the energization of the release magnet. Also included in the test link/xox' repeater are two relays R240 and R200, the second of which is arranged to respond to the application of ground potential to the control conductor C|04 of thev line 245 and functions to project ringing current out over the associated line 245. This ringing current is derived from a ringing current generator schematically indicated at 210. The relay R240 functions to disconnect the ringing current generator from the line 245 a short time interval after the relay R250 functions to connect the ringing current generator thereto. More particularly, the relay R250 is provided with a vibrating reed type of armature RA255 which is weighted at one end thereof in a well-known manner so that, when R250 operates to move RA254 into engagement with RA255, the last-mentioned weighted armature vibrates for an interval to prevent the relay R240 from being sufficiently energized to operate. Also included in the repeater is an additional relay R| which is of the polarized type, this relay being provided to control the energization of a signal device lo'cated at the operator's telephone station in the remote manual oillce in the manner described in detail hereinafter. Specifically, the relay R|50 is soarranged that it is operative from one of its two p0- sitions to the other when the polarity of' the current flowing through the two repeater windings |83 and |34 and over the conductors of the trunk line |35 to certain of the non-numerical and numerical switches provided in the automatic exchange is reversed.

The apparatus provided at the operators station in the distant manual oflice, wherein the line 2`45 is terminated, comprises a repeating coil 225, an answer jack 2|5, a ringing key 205, al dialing key 2|0, a drop or signal device 233, an impulsing .device 22|, a disconnect supervisory lamp 232, and a relay R230 for controlling the lamp 232, all connected and arranged in the manner illustrated and operative in the manner pointed out in detail hereinafter. It is mentioned here that the relay R230 which controls the energization of the signal lamp 232 is connected and arranged to Vbe energized in series withthe line relay R|50 provided in the automatic exchange over a circuit including the line 245. The relay R230 is of the marginal type such that it is only sufficiently energized to operate when the resistor |52 is excluded from its operating circuit.

Referring now more particularly to the operation of the apparatus to extend `a connection from one of the regular automatic subscribers lines, such, for example, as the line |0|, to one of the substations associated with the line 245, and assuming that the line switch |00 operates to extend the connection from the calling substation C to the selector switch |05, when a predetermined digit is dialed at this substation, the selector switch noted is caused to operate automatically to select an idle one of the connector switches in the group including the switch ||0. Assuming that the last-mentioned switch is the first available idle switch of the selected group, when the calling subscribers loop circuit is extended thereto, the control apparatus embodied therein operates to condition the switch to reemessi nectorl switch further operates to select the particular called line 245 from the selected group of lines. As pointed out more in detail hereinafter, if the selected line 245 is busy, ground potential is present on the control conductor C|04 thereof so that the connector switch, upon testn'ing the condition of the line and'nding the line busy, operates to return busy tone to the calling subscriber to indicate that the desired connection can not immediately be established. If, on the other hand, the selected .called line is idle, battery-potential as extended through the winding of R250 and by way of Cl03, RC|42, and RA|4I is applied to the control conductor C|04. With -the line idle, the connector switch operates to extend the calling subscribers loop circuit through to the repeater |80, thereby to energize the polarized relay Rl60. Simultaneously with the switching-through operation, ground is applied to CI04 in the connector switch to cornplete a circuit for energizing the relay R250', this circuit extending from ground on the control conductor noted by way of RAMI, RCI42, C|03` and the winding of R250 to battery. Upon operating, the relay R250 completes a holding circuit for itself, this circuit extending from ground as applied to C|04 by way of RA256 and the winding of R250 to battery. At RA25I and RC253, the relay R250 `completes a. circuit for energizing the signal device or drop 233 provided in the distant manual office, this circuit extending from the ungrounded terminal of the ringing current generator 210 by way of RC242, RA24I, RC253,

RA25I, the conductor 245, the switch springs 2|6 and 2|8, the winding of the drop 233 and the condenser 234 tothe grounded terminal .of the ringing current generator. Through the operation of its armature RA254, the relay R2 50 startsI the weighted armature RA255 vibrating. After an interval required forthe amplitude of vibrationy of RA255 to die down, this armature settles into engagement with RA254 to complete an obvious circuit for energizing the relay R240. Upon operating, the relay R240 interrupts, at RA24I and RC242, a point in the above-traced circuit for Aconducting ringing current over the line 245 to the operators position in the distant manual omce. At-RA24I and RC243, the relay R240, upon operating, prepares a point in the talking circuit to be completed between the calling subscribers substation and the operators telephone station. I

'I'he polarized relay R|60 operates when energized over the calling subscribers loop circuit to interrupt, at RAISI, the path normally shortvtraced circuit for energizing the drop 233. At

the springs 2|6 and 2|1, a circuit is completed for energizing R230 in series with RI50, this circuit extending from ground at the lower terminal of the repeater winding 228 byway oithis winding, the Winding of R230, the swltchsprings 2I3 and 2I2, the switch springs 208 and 206, the springs 2I'I and 2|6, the conductor 245,.RA25|, RC253, RA24I, RC243, C| 02, the repeater Winding |8 the resistor |62, and the winding of R|50 tobattery. Due to the inclusion of the resistor I 62 in this circuit, the relay R230 is notsuiilciently energized to operate when the circuit lis completed. The relay R|50, however, is suiciently energized to operate and, upon operating, completes, at RA|5| and RCI53, an obvious circuit for energizing the slow-to-release hold relay'Rl40. When ythe last-mentioned relay operates, it interrupts, at RAMI and RCI42, a point in the above-traced operating circuit for R250 and applies, at RA|4I and RCI 43, multiple ground to the control conductor C|04, thereby to complete a multiple holding circuit forR250. At RAI44 and RC|45, the relay RI'40 opens a point in the circuit, traced hereinafter, for energizing the release magnet |14 and, at RA|44 and RC|46, it prepares a point in the circuit, traced hereinafter, for energizing the operating magnet |13 of the switch |10, this latter circuit now being held open at the operated armature RAI 5| of the relay R I 50.

When the operator answers the call, a talking circuitv is completed between her telephone and the calling subscribers substation, which circuit minal of the repeater winding 228 by way of this winding, the condenser 235, the switch springs 2I3, 2|2, 208, 206, 2|'| and 2|6,'.the line conductor 245, RA25I, RC253, RA24I, RC243, C|02, the repeater winding |8I, thev condenser |85 and the y repeater winding |82 to ground.

Upon conversing with the calling party to ascertain which of the rural substations is desired, the operator in the manual oiiice 200 may proceed to ring the desired substation by operating the ringing key 205 in accordance with the particular code corresponding to the called substation. Each time the key'205 is operated toits off-normal position, the springs 2 06 and 208 are` opened to prevent ringing current from being projected through the winding 228 of the repeater 225 and the springs 206 and 201 are closed to project ringing current out over the line 245.

Assuming that the substation A is being called,

the key 205 isfactuated in accordance with the coded signal identifying thissubstation. The path which the ringing current traverses in energizing the ringer or signal device at the substation A extends from theungrounded terminal of the ringingv generator, not shown, by .way of the springs 201, 206, 2||f, and 2|6, the line 245, the condenser 236 and the ringer at the called substation to the grounded terminal of the ringing current generator. A portion oi.' this current is also conducted through'the ringing devices at the other substations associated with the line 245, but, due to the coded nature of this current, the subscriber at the called substation is informed that his substation is being called to the exclusion of the other substations. During each period when ringing current is being projected over the line 245, the line relay R|50 is held energized over a circuit slightly different from its operating circuit as traced above. Specifically, this holding circuit for RI50 extends from the grounded terminal of the ringing generator, not shown, by

way o1' this generator. the switch springs 201,

206, 2|1 and 2|5, the line conductor 245, RA25I, RC253, RA24I, RC243, C|02, the repeater winding I3I, the resistorA |32 and the winding of RI50 to battery. Obviously. at the end of each ringing period, the operating circuit, as traced previously, is recompleted through the closure of the springs 206 and 203.`

When the call is answered at the called substation A, the desired talking connection is fully completed between the calling and called substations. The operator does not remove the answer plug from the jack 2|5 until after the conversation is terminated. If, at the end of the conversation, the calling subscriber at the substation C is the rst to hang up, the operated switch train comprising the connector switch I I0, the selector switch |05 and the line switch |00 is released in the manner set forth above. When the calling party hangs up `the polarity of the current traversing the winding of RISO is reversed, causing this relayi to restore to shortcircuit, at RAIBI, the resistor |32. Asia result, the resistance of the circuit including the serially connected windings of R230 and RI50 is lowered and the current traversing the winding of R230 is increased sufficiently to cause this relay to operate. Upon operating, the relay R230 completes, at RA23I, an obvious circuit iforr energizing the signal lamp 232, thereby to indicate to the operator that the line 245 is no longer occupied with a call. The operator may now release the line for further use by removing the answer plug from the jack 2|5, thereby to interrupt, at the springs 2|6 and 2|1, the circuit over which the windings of R230 and RI50 are energized in series. When this circuit is interrupted, the relay R230 restores to open the circuit for energizing the lamp 232, and the relay RI50 restores to open, at RA|5I and RCI53, the operating circuit for R|40. At RA|5| and RCI52, the relay RI50, upon restoring, completes the -above-mentioned circuit for energizingk the operating magnet |13, this circuit extending from ground at the lower terminal of the repeater winding |32 by Way of RAISI, RCI52, RAI44, RCI46, RAI3| and the winding of the magnet |13 to battery. The relay RI40 restores, after an interval, to interrupt, at RAI 4| and RC |43, the holding circuit for R250 and to remove ground from the control conductor CI04, thereby to mark the line 245 as idle in the bank contacts of the connector switches to which the4 trunk |35 extends. At RA|44 and RCI45, the relay RI 40 interrupts the above-traced circuit for energizing the magnet |13, causing this magnet to be deenergized. As a consequence of the energization and deenergization of the inagnet I13, the w'lper |12 is stepped one step and the off-normal springs |15 are closed. When the springs |15 are closed a circuit is completed for energizing the release magnet |14, this circuit extending from ground at the lower terminal of the repeater winding |82 by way of RAISI, RC|52, RAI44, RCI45, the off-normal springs |15 and the winding of the magnet |14 to battery. When energized over this circuit, the magnet I 14 attracts its associated armature, not shown, to cause the wiper |12 to be returned to its home position. When this occurs, the oil-normal springs |15 are opened to interrupt the circuit for energizing the magnet |14.

When R250 restores, it opens, at RA25I and RC253, a point inthe above-traced circuit for energizing the drop 233 and interrupts, at RA254 and RA255, the operating circuit for R240. The relay R240, upon restoring reprepares, at RA24I and RC242, a point in the circuit for energizing the drop 233. Following the restoration of R240. the connection is entirely released.

Referring now to the operation of the apparatus to set up a connection between the line 245 and o ne of the automatic subscribers lines on a call initiated at one of the rural substations, such, for example, as the substation A; when the magneto generator at the last-mentioned substation is operated in the usual manner, ringing current is projected over the line 245 to cause the operation of the drop 233, thereby to indicate to the operator in the manual oilice 200 that a call on the line 245 awaits her attention. The operator answers the call inthe manner pointed out above, that is, by inserting the answer plug terminating her telephone set in the jack 2|5, thereby completing/a talking connection to vthe calling subscribers substation. When the call is answered in this manner, a circuit is completed for energizing the relay RI50 and the relay R230 in series, this circuit being substantially similar` to that traced previously but extending over the line conductor 245 and by way of RA25| and RC252 to C|02, rather than by Way of RC253, RA24| and RC243. In the present case, the relay RI50 is restored and the resistor |62 is short-circuited, so that the current owing overthev circuit noted is of a value sumcient to cause the operation of R230 as well as the operation of RI50. When R230 operates, it completes the above-mentionedcircuit for energizing the signal lamp 232, and,`when RI50 operates, it completes the above-mentioned circuit for energizing the slow-to-release relay R|40. When RI40 operates, it opens, at RA|4I 'and RC|42, a point in the operating circuit for R250 and, at RA|4| and RCI43, appliesground to the control conductor C|04, thereby to mark the line 245 as busy in the bank contacts of the connector switches to which the trunk line |35 extends. At RA|44 and RCI46, the relay R|40 prepares a point in the circuit, traced abovef'for energizing the operating magnet |13.

Upon ascertaining the number of the substation desired by the calling party, the operator may actuate the dial key 2|0 to the off-normal position'to connect the impulsing device 22| in circuit. with the line relay RI50. More particularly, when this key is operated to its oli-normal position, the previously traced circuit for energizing R230 is interrupted at the springs 2|2 and 2|3, and an alternative circuit extending from ground at the lower impulsing spring oi.' the device 22| and substantially similar to that traced above is completed at the springs 2|| and 2|2 for holding RI50 energized. Following the operation of the key 2|0 to its off-normal position, the operator may actuate the dial controlled impulsing device 22I in accordance with the directory number of the desired subscribers substation. Y

As pointed out in the introductory portion of the specification, it is necessary to dial a prex digit at the operators telephone station beforel the calling line is switched through to cause the line switch I I5 to operate. With the arrangement illustrated, a preiix digit comprising ten impulses is required. At the -beginning of the ilrst impulse of this digit, the circuit over which the line relay R|50 is being held energized is interrupted at the springs of the impulsing'de- "vice 22| and the line relay restores to complete,

at RA|| and RC|52, the above-traced circuit for energizing the operating magnet |13 of the switch |10. Upon being energized over the above-traced circuit, the magnet |13 attracts its associated armature, not shown, to condition the associated ratchet and pawl mechanism to step the wiper |12 one step or into engagement with the first contact of the set |1 I. When, at the end of the ilrst open circuit pulse, the impulsing springs of the device 22| are closed to recom- 'plete the circuit for energizing the line relay R|50, the last-mentioned relay operates to interrupt the above-'traced circuit for energizing the magnet |13. Upon being deenergized, the magnet |13, in cooperation with its associated ratchet and pawl mechanism, steps the wiper |12 one step or into engagement with its associated rst contact. When the wiper |12 takes this first step, the off-normal springs are closed to prepare the circuit, traced above, for energizing the release magnet |14. During each succeeding impulse occasioned by further operation of the impulsing device 22|, the wiper"|12 of the switch |10 is caused to advance one step, in a manner identical with that just described. At the end of the ten impulses comprising the preilx v digit, the wiper |12 is, therefore, advanced into engagement with its associated tenth contact, assuming the impulsing conditions of the line are such that the line relay R|50 responds to the impulses in a satisfactory manner.

Immediately the wiper |12 is advanced into engagement with the tenth contact of the set |1|, an obvious circuit is completed for energizing R|30. When R|30 operates, it interrupts, at RA|3|, a. point in the above-traced circuit for energizing the magnet |13, thereby to prevent the switch |10 from responding to any further impulses dialed at the operators station. At its armatures RA|32 and RAI33, the relay R|30 completes a loop circuit for initiating the operation of the line switch ||5 to selectfan idle one of the selector switches. The last-mentioned circuit may be traced from the lower terminal of the repeater winding |84 by way of the winding of R|60, the repeater winding |83, RA|33, one side of the trunk line |35, the windings oi' the line relay in the line switch ||5 connected in series with battery, the opposite side of the trunk line |35, RA|32 and RAI54, back to thek lower terminal of the repeater winding |84. yThe polarity of the current iiowing in this loop circuit, which current is supplied by the battery connected in series with the two windings of the line relay, conventionally provided in the line switch ||5, is such that the polarized relay R|60 does not operate.

When the above-mentioned loop circuit is completed, theline switch ||5 operates to select a trunk leading to an idle selector switch. As-

suming, for example, that the selector switch is the first available idle switch, `the line switch ||5 functions to switch the above-traced loop circuit through to the selector switch |20, thereby to lcause this switch to be conditioned to respond to the second series of impulses dialed at the operators station, and dial tone to be returned over the established loop to the operator. The line relay R|50 follows the impulses of the second digit in the lsame manner as is pointed out above with reference to the operation of the I apparatus during the dialing of the preiix digit and, at its armature RAI54, it repeats the impulses to the selected selector switch |20. The last-mentioned switch' responds in the usual manner by operating its wipers to a position opposite the level of bank contacts terminating the trunks leading to the groupfof connector switches having access to the called line. If it be assumed, for example, that the substation C is the particular substation desired by the calling substation, the selector switch will respond to the impulses of the second digit to select the group of trunks respectively extending to the connector switches in the group including the switch |25. Following the dialing of the second digit, the selector switch |20 automatically operates, in a well-known manner, to select the first available idle switch which, in the present case, may be assumed to be the switch |25. When this connector switch is selected, the above-mentioned loop circuit is switched through to vcause the switch to be conditioned to respond to the impulses of the third and fourth digits dialed at the operators station. T'he connector switch noted, namely, the switch |25, responds to the impulses of the third and fourth digits by rst selecting the group of ten lines including the called line |0| and then selecting the particular called line of the selected group in a vwell-known manner. The connector switch also operates to test the condition of the called line, to return busy tone over the loop to the operators telephone in the event the called line is busy, and to apply ringing current tothe called line in the event this line is idle.

Following the completion of the dialing operation, the operator at the manual oflice 200 restores the dial key` 2|0 to its normal position to recomplete the previously traced circuit for energizing R230 in series with the line relay R|50. When this operation is performed, and if the called line Vis busy, the operator will receive busy tone and will thus be informed that the desired connection can not immediately be established. On the other hand, if the called line is idle, ringback tone will be received by the operator to indicate that the desired called substation is beingr'ung. I

When the call is answered at the called' substation C, battery is reversed back over the loop extending to the repeater |80, thereby to reverse the direction of current iiow through the winding of the polarized relay R|60. As a consequence, the relay R|60 operates to interrupt, at RAISI, the path short-circuiting the resistor |62, thereby to insert this resistor in the series circuit over which R|50 and R230 are being held energized. The resulting decreasein the magnitude of the current in this circuit causes R230 to restore to interrupt, at RA23 I, the circuit for ener gizing the signal lamp 232. It will, of course, be understood that, when' the call is answered at the called substation, the desired conversational circuit is completed between the calling and called parties. Here again the operator retains the answer plug in the jack 2|5 until the conversation is terminated.

When the conversation is terminated and the called party hangs up, battery is again reversed over the loop extending back to the repeater |80 to cause the restoration of the polarized relay R|60. As a result, R|60 restores to short-circuit, at RAIVSI, the resistor |52, thereby to cause the reoperation of the relay R230 and the reenergization of the signal lamp 232. The energization of this lamp indicates to the operator that the established connection is ready to be released. The release of the connection is effected in a manner similar to that described above. Thus. when the answer plug is removed from the jack 2li, the series circuit including the two windings of R|50 and R230 is interrupted and these two relays restore. The relay R230, upon restoring, interrupts the circuit for energizing the signal lamp 232, and the relay R|50, upon restoring, interrupts at RA|54, the loop circuit extending to the line switch H5 and, at RA|5|, the circuit over which RI40 is being held energized. When the relay RI40 restores, it completes, at RA|44 and RCI, the above-traced circuit for energizing the release magnet |14. The release magnet now attracts its armature, not shown, to cause the wiper 12 to be returned to its normal position. When the wiper |12 is disengaged from its associated tenth contact, the operating circuit for R|30 is interrupted and this relay restores to reprepare, at RAI3I, a point in the circuit for energizing the operating magnet |13 and to interrupt, at its armatures RA|32 and RAI33, further points in the loop circuit extending to the line switch ||5.

When the switch |10 is returned to its normal position, the ofi-normal springs |15 are opened to interrupt the operating circuit for the release magnet |14. The slow-to-release relay RI40, upon restoring, removes ground, at RA|4| and RC|43, from the control conductor CI04, thereby to mark the line 245 as idle in the bank contacts of the connector switches to which the trunk line |35 extends. When the loop circuit extending to the line switch ||5 is interrupted, the operated switch train comprising the switches H5, |20 and |25 is released in a manner substantially similar to that pointed out previously. Following the restoration of R|30, RI40 and R|50 and the restoration of the switch |10 to normal, the apparatus is completely released and in readiness for further use.

Although a connection between two substations connected to the line 245 may be performed directly in the conventional manner through the proper actuation of the magneto generator at the calling substation toA code ring the desired called substation, such connections are preferably completed with the assistance of the operator in the manual office 200. The advantage of enlisting the operators assistance in completing a reverting call connection resides in the fact that the operator, by retaining her answer plug in the jack terminating the line, can guard the line against seizure by-one of the connector switches in the automatic exchange, whereas the line is unguarded when such a call is directly completed. 1f, for example, a subscriber at the substation A desires a connection with the substation B, the call is initiated in the manner pointed out above, that is, through the operation of the magneto generator provided at the substation A. The resulting operation of the drop 233 indicates to the operator in the manual oflice-that a call has been initiated on the line 245. The call is answered in the usual manner by inserting the answer plug in the jack 2 l5 to establish a talking connection by way of the line 245 to the calling substation A. When the answer plug is inserted in the jack 2|5, the above-traced circuit is completed for energizing-RIM in series with R230 and, since at this time the polarized relay R|60 is restored, both of the'relays RI 50 and R230 operate. When the relay R|50 operates, it completes the operto the control conductor CI04, thereby to marl:l

the line 245 as busy in the bank contacts of the connector switches to which the trunk line |35 1 extends.

Upon ascertaining the party desired by the calling subscriber, the operator may actuate the ringing key 205 to project ringing current back over the line 245 in the manner described previously. 'I'he coded nature of this current indicates to the called subscriber that his substation is being called and informs the parties at the other substations connected to the line that the call is intended for the substation B. Obviously, when the call is answered at the called substation, the desired conversational connection is established between the two substations A and B. Here again, the operator retains the answer plug in the jack 2|5 for the purpose of holding the relays RI40 and R|50 operated, thereby to maintain the line 245 guarded against seizure by one of the connector switches provided in the automatic exchange. In this case, it is necessary for the operator to challenge the connection at intervals to determine whether the conversationvbetween the calling and called parties is terminated. This is true for the reason that no means are provided for indicating when theparties at the calling and called substations hang up to clear the line. Upon ascertaining that the conversation is terminated, the operator may release the connection by withdrawing the answer plug from the jack 2|5, thereby to interrupt the series circuit including the windings of R230 and R|50. Upon restoring, R|50 interrupts the operating circuit for RI40 and completes, at RAI 5| and RCI 52, the above-traced circuit for energizing the operating magnet |13. Shortly thereafter and when RI40 restores, ground is removed from the control conductor C|04 to mark the line 245 as idle and the circuit for energizing the magnet |13 is interrupted. As a result of the energization and deenergization of the magnet |13, the wiper |12 of the switch 10 is stepped one step or into engagement with its associated iirst contact, and the ofi-normal springs |15 are closed. With the two relays R|50 and RI40 restored and when the springs |15 are closed, the above-traced circuit for energizing the release magnet |14 is completed. The resulty ing operation of this magnet causes the switch |10 to be restored to normal and the springs |15 to -be opened to interrupt the circuit for energizing the release magnet. Thus, the connection is entirely released and the line 245 is in readiness for use on another call.

From the foregoing description it will be apparent that a connection can only be routed i over the line 245 and by way of the automatic switching equipment in the automatic exchange by dialing a predeterminedl preiix digit at the operators telephone station. It will also be noted that when a reverting call is initiated on the line 245, the relay R|30 is not energized and, hence, none of the regular automatic switching equipment is assigned to the use of the line. If for any reason the manual oiiice operator, in initiating a call to one of the automaticv subscribers substations, fails to dial the required prex digit of ten impulses, or the impulsing conditions of the line are such as to preclude a faithful response thereto by the line relay Rl50, the minor switch 10 will not be operated to its tenth offnormal position to cause the operation of R| 30,

Iii

in response to the impulses of1the1prex digit. Hence, the loop circuit to theline switch |15,

will not be completed and none of the. regular automatic switching equipment will be assigned to the use of the calling line.

It will further be apparent from the foregoing description that, with the arrangement illustrated in Figs. 1 and 2, the selective signaling o f the substations on the line 245 is entirely under the control of the operator in the manual ofhce 200. With the arrangementillustrated in Figs. 3 and 4, on the other hand, provisions are made whereby a calling automatic subscriber, by dialing a ringing digit following the usual line selecting digits, may cause the proper coded ringing current, corresponding to the desired substation, automatically to be projected over the line to signal the desired substation. By virtue of this improved arrangement, the operators assistance in completing calls originated at an automatic substation on a line terminating in the automatic exchange is not required. However, on calls originating at substations provided on the line extending between the automatic and manual oiilces which are not equipped for automatic service, the intervention or assistance of the operator in the manual oilice is Vnecessary in setting up the desired connections.

Referring now more particularly to the apparatus provided in the system illustrated in Figs. 3 and 4v in association with the multi-party line 486, it is pointed out that the equipment located at the operators telephone station in the manual office 480 may be identical with that described previously with reference to the corresponding equipment provided for terminating the line 245 of the system illustrated in Figs. 1 and 2. The repeater or test link located in the automatic exchange and terminating the other end of the line 486 comprises a repeating coil 315 connected by Way of a trunk line 346 to certain ofthe numerical and non-numerical switches in the automatic exchange; a line'or impulsing relay R415; a slow-to-release hold relay R430; an impulse correcting network comprising the three relays R420, R440, and R450, and a switching-through relay R460 which is under the control of an impulse responsive switch 410. The relay R450 is an impulsing relay which responds to the operation of R415 and functions to repeat impulses to the switch 410 and to the automatic switches constituting the regular automatic switching equipment provided in the exchange. The switch 410 is of the well-known minor type and comprises a single set of bank contacts 414, a wiper 415, an operating magnet 41| for driving the wiper 415 over the contacts of theset 414, a

release magnet 412, and oil-normal springs 413 for controlling the energization of the release magnet. As pointed out in detail hereinafter, the equipment just described, namely, that illustrated in Fig. 4, is the portion of the repeater which operates when a connection is being routed from one of the substations associated with the line 486 or from the operators telephone 'station to one of. the other lines terminating at the automatic exchange. On calls routed by way 'of the automatic switching equipment to a substation on the line 486, the apparatus illustrated in Fig. 3 is primarily the apparatus which enables the desired connections to be established..v

More particularly, the apparatus illustrated in Fig. 3 is provided for controlling the selection of a ringing code correspondingy to a desired substation on the line 486. In brief, this apparatus tatxmprises a switching relay R320, a line relay Alkle-a, slow-to-release hold-relay R330, a pair be ofv any desired commercial construction, al-

though preferably the ringing interrupter 395 is of the form described and claimed in copending application Serial No. 203,474, Clarence'E. Lomax, filed April 22, 1938. This interrupter functions to apply to the ilve ringing current conductors terminating at the contacts of the code selector switch the 'voltage developed by the ringing Ycurrent generator for coded intervals which are different for each of the ringing current conductors. 'I'he code selector switch is preferably of the well-known minor type and comprises a single set of bank contacts 38|, a wiper 382, an operating magnet 319 for driving the wiper 382 over the contacts of the set 38|, a release magnet 318, .and oi-normal springs 380 for controlling the energization of the control relay R340. l

For the purpose of marking the line 486 as busy in the bank contacts of the numerical switches having access thereto when this line is occupied with reverting calls, there is provided a novel and improved arrangement comprising the two relays R350 and R360 and the impulse gen-I erator 385. 'I'he relay R350 is so constructed that it operates when its upper winding is energized with direct current or with alternating ringing y current. 'I'iie generator 385 may be of any wellknown construction which inchdes means for alternately applying ground pulses to the time pulse leads C303 and C304 at spaced intervals. If desired, it may comprise a commutator driven by a synchronous motor through a gear reduction box and including grounded segments suitably arranged to engage brushes respectively terminating the leads C303 and C304.

Referring now more particularly to the operation of the apparatus illustrated in Figs. 3 and 4 to set up a connection between one of the automatic subscribers substations, as, for example, the substation E connected to the 1ine30l, and one of the substations connected to the line 486, and assuming that the line switch 300, the selector switch 305 and the connector switch 310 are successively operated in the usual manner to select the called line 486; when the connector switch -3I0 completes its operation and if the line 486 is idle, ground is applied to the control conductor C482 in the connector switch andthe calling subscribers loop circuit is extended by Way of the trunk line 346 to the repeater 315. When ground is applied to C482, a circuit is completed forenergizing R320, this circuit extending and the winding of R320 to battery. Upon operating, the, relay R320 short-circuits at RA323 the upper winding of R350, thereby to exclude this kwinding from the ta1k1ngcircuit ultimateiy to be established. At RA323, the relay R320 opens im l a point in the circuit, traced hereinafter, for energizing R415.' .At RA32I and RA322, the relay R320 completes a circuit for energizing R325, this circuit extending from ground at the lower terminal of the upper winding of R325 by way are arranged to switch through on a call of the character under consideration. When energized over the above-traced circuit, the relay R325 operates to complete, at RA323 and its associated lower contact, an obvious circuit for energizing the slow-to-release hold relay R330. When R330 operates, it applies, at RA33I, multiple ground to the control conductor C482; opens, at RA332 and its associated upper contact, a point in the circuit, traced hereinafter, for energizing the release magnet 313; and prepares, at RA332 and its associated lower contact, a circuit for energizing R335 in parallel with the rotary switch operating magnet 319. At RA333, the relay R330 applies ground to the ringing interrupter start conductor C398, thereby to initiate the operation of the interrupter 395. Eollowing the" operation of R330, the apparatus illustrated in Fig. 3 is conditioned to respond to the impulses of the code selecting digit dialed at the calling substation. During each impulse, the calling subscribers loop circuit is opened for an interval, in the usual manner, and the line relay R325 follows the impulses by alternately restoring and operating. Each time R325 restores, the abovementioned circuit is completed for energizing R336 in parallel with the magnet 319, this circuit extending from ground at RA323 and its associated upper contact to RA332 and its associated lower contact, where it divides, one branch extending by way of the winding of R335 to battery and the other branch extending by way of RA343 and the winding of the magnet 319 to battery. Each time the magnet 319 is energized,

it attracts its operating armature, not shown, to

condition the associated ratchet and pawl mechanism to step the wiper 332 one step and thereafter, when it is deenergized, the associated ratchet and pawl mechanism performs the stepping operation. When the wiper 332 takes its first step, the off-normal springs 380 are closed to prepare a circuit, traced hereinafter, for energizing R340. It will be understood that, at the end of the code selecting digit, the wiper 382 is left standing in engagement with the contact of the set 38| corresponding to the particular code identifying the called substation. For example, if the substation A' is being called and the code call designating this substation corresponds to the code of the ringing voltage applied to the third conductor terminating at the set 38|, the code selecting digit will necessarily comprise three impulses so that, at the conclusion thereof, the wiper 382 will be left standing in engagement with its associated third contact.

Shortly-following the conclusion of the code selecting digit and with R325 in its operated p0- sition, the relay R335 restores to complete the above-mentioned circuit for energizing R340, this circuit extending from ground at RA338 by way of RA342, the oiT-normal springs 380 and the winding of R340 to battery. Upon operating the relay R340 completes, at RA34I, a holding circuit for itself, this circuit extending from ground at RAMI by way of RA342, the off-normal springs 380 and the winding of R340 to battery. At RAMI, the relay R340 interrupts a point in the above-traced impulsing circuit extending to the operating magnet 319 and, at RA344, the relay R340 further prepares the circuit, mentioned above, for energizing the release magnet 318.

The arrangement of the apparatus is such that ringing current is projected over the line 486 during a ringing operation for a predetermined number of code cycles only, following which the ringing current path is interrupted. More particularly, a ground pulse is applied to the pick-up lead C383' at the beginning of each code cycle by the interrupter 395, and when the first ground pulse is applied to C366 following the operation of R340, a circuit for energizing R365 is completed, this circuit extending by way of RA345, RA361 and its associated upper contact, and the lower winding of R365 to battery. When its lower winding is energized over the circuit just traced, the relay R385, which is of the two-step type, only partially operates to complete, at RA366, a path for short-circuiting its upper winding, this path extending from ground as applied tothe pick-up conductor C366' by way of RA345, RA361 and its associated upper contact, the upper winding of R365, and RA386 to the grounded control conductor C482. At the end of the ground pulse applied to C386', the above-traced shortcircuiting path is obviously interrupted, permitting the two windingsof R365 to be energized in series. The relay R365 now completes its operation and, in so doing, interrupts, at RA361 and the associated upper contact, a point in the abovetraced circuit for energizing its lower winding. At RA368 and its associated upper contact, the relay R365 completes a path for projecting coded ringing current out over the called line 486. The path of this current extends from the ungrounded terminal of the ringing generator 390, by way of the ringing interrupter 395, the ringing current conductor terminating at the third contact of the set 38|, the wiper 382, RA316 and its associated upper contact, RA388 and its associated upper contact, the line conductor 486, the condenser 481 and the ringer, not shown, at the called substation A', to the grounded terminal o'f the ringing current generator. Portions of the ringing current also ilow through the ringing devices individually provided at the other substations associated with the line 483, but the coded nature of the ringing indicates to the respective parties that only the substation A' is being called. It will be noted that a portion of the ringing current also flows through the drop provided at the operators station in the manual oiiice 430 to actuate this device. As is well known, this device operates in the manner of a buzzer to inform the operator that her assistance is not needed in completing the desired connection.

At the end of the rst ringing cycle, the ringing interrupter 395 applies a second ground pulse to the pick-up conductor 386', thereby to complete a circuit for energizing the lower winding of R310, this circuit extending by way of RA345, RA361 and its associated lower contact, RA312 and its associated upper contact and the lower winding of R310 to battery. 'I'he `relay R310, like the relay R365, is of the two-step type and, hence, it only partially operates when its lower winding is energized. Upon partially operating, the relay R310 completes, at RA31I, a path for short-circuiting its upper winding, which path is substantially identical to that, traced above, for the upper winding of R355. At theend of the ground pulse applied to the pick-up conductor, this short-circuiting path is interrupted, permitting the two windings of R310 to be energized in series. The relay R310 now completes its operation to interrupt, at RA312 and its associated upper contact, the above-traced circuit for energizing its lower winding and to prepare, at RA312 and its associated lower contact, a circuit for energizing the winding of R315. During the interval between the end of the second code -cycle and the beginning of the third code cycle, and when ground is again applied to the pick-up conductor C365', the above-mentioned circuit is completed for energizing the winding of R315, this circuit extending by way of RA345, RA351 and its associated lower contact, RA312 and its associated lower contact, RA318 and the winding of R315 to battery. When its winding is energized over the above-traced circuit, the relay R315 first closes the "X contacts associated with RA311 to complete a holding circuit for itself, this circuit extending from the grounded control conductor C482 'by way of RA311 and the winding of R315 to battery. Shortly after the completion of this holding circuit, the relay R315 interrupts, at RA318, its operating circuit as traced above and, at RA318 and its associated upper contact, interrupts a point in the above-traced path for projecting ringing current over the called line 486. At RA316 and its associated lower contact, the relay R315 extends the talking loop to the called substation A. When the call is answered at the called substation, the desired conversational circuit is fully established. The portion of this circuit extending between the calling substation E and the repeater 3I5 will readily be apparent from an inspection of the drawings. 'I'he remaining portion of this circuit, namely, that extending from the repeater 3I5 to the called substation A, extends from ground at the upper terminal of the repeater winding 3I5, by way of this winding, the condenser 318', the repeater winding 3|1, RA323, RA318, RA388, the line conductor 485, the condenser 481 and the telephone substation equipment at the substation A', back to the ground return side of the line.

The release of the connection as established between the substations E and A', in the manner just described, is entirely under the control of the party at the calling substation .E. More particularly, when the calling party hangs up, the three switches 3I0, 305 and 300 vare released, in the order named and in the manner pointed out previously. When the call is cleared out at the calling substation, multiple ground is removed from the control conductor C482 in the connector switch 3 l 0 and the loop circuit over which the line relay R325 is being held energized is interrupted. When R325 restores, it interrupts, at RA328, the operating circuit for the hold relay R330, causing the last-mentioned relay to restore, after an interval, to reanove ground from the control conductor C482 at its armature RA33I. At RA332, .the relay R330, upon restoring, completes the above-mentioned circuit for energizing the release magnet 318, this circuit extending from ground at RA328 by way of RA332 and its associated upper contact, RA344 and the winding of the magnet 318 to battery. When the magnet 31,8 is energized, the wiper 382 is returned to its home position in a well-known manner, at which time the off-normal springs 380 are opened to interrupt the holding circuit for- R340. When R340 restores, it opens a further point in its holding circuit, reprepares the circuit for energizing the operating magnet 319, and interrupts, at

RA344. the operating circuit for the release magnet 318. n

When R330 restores to remove ground from the control conductor C482, battery potential is impressed on the control conductor to mark the line as idle. More specically, the marking path extends from battery by way of the winding of R320, RC353, RA35I, C483, RC432, and RA43I to the control conductor C482. The removal of ground from C482 results in the interruption of the common portion of the holding circuits for the three relays R355, R310 and R315, causing all oi.' these relays to restore. Following the above-described sequence of operations, the connection is entirely released, the line 485 is marked as idle, and the apparatus is in readiness for further use.

Although, in the operation of the apparatus as just described, the ringing operation isvautomatically performed in response to the dialing of the proper code selecting digit at the calling substation, it will be understood that the operator in the manual oiiice 480 may, if desired, be called upon to signal the desired called substation by ringing back over the called line. More particularly, the code of the ringing current applied to one of the ringing current conductors extending to the contacts of the contact set 38| may correspond to the coded ring identifying the operators telephone station as the station being called. If, for example, the code of the ringing voltage applied to the ilrst conductor terminating lat the first contact of the set 38| is the code identifying the operators telephone station, and the assistance of the operator in completing the call is desired, the calling party may, by dialing a code selecting digit consisting of one impulse, cause ringing current to be projected over the line cf the proper code to indicate to the operator-that her station is being called. It will be lunderstood that the operation of the ringing apparatus to project ringing current of the selected code over the called line to the operators station is in all respects identical with the operation of the apparatus as described above. Also, the manner in which the operator answers thev call and operates her ringing key to project coded ringing current of the proper code back over the called line may be substantially similar to that described above with reference to the system illustrated in Figs. 1 and 2.

'Ihe manner in which a connection is completed between one of the rural substations associated with the line 486 and one ofthe automatic subscribers substations on a call initiated at the rural substation depends upon the nature oi the last-mentioned,substation. More particularly, if the calling rural substation is of the fully automatic type and is equipped withan impulsing device, the calling party may cause the desired connection to be set up without any assistance on the `part of the operator in the manual cnice 480. On the other hand, if the calling substation is of the magneto type andis not provided with impulsing means, the assistance of the operator in the manual oiiice is necessary in securing the desired connection. For example, if a party at the substation A desires a connection with one of the automatic subscribers substations, as, for example, the substation E, the calling party may initiate the call by actuating the magneto generator provided at the substation A in accordance with the code identifying the cperators telephone station in the manual ofllce 480. The resulting operation of the signal device provided at the operators station indicates to the operator that a call awaits attention. A'portion of the ringing current projected over the line 486 is conducted through the upper winding of R350, causing this relay to operate. When the call is answered, and as was explained above vwith reference to the apparatus illustrated in Fig. 2 of the drawings, a talking connection is established between the operators telephone and the calling substation. Also, ground is applied to the line conductor 486 to complete a circuit for energizing the relay R4l5, this circuit extending from ground on the conductor noted by way of RA368 and its associated lower contact, RA354, the repeater winding SI1, RA323, C48| and the winding of R4l5 to battery. When its upper Winding is energized by the ringing current projected over the line 486 the relay R350 rst attracts its armature RA355 to complete, at the "X contacts associated with this armature, an obvious holding circuit for itself. Thereafter, the relay R350 completes, at RA354, an obvious path for short-circuiting its upper winding, thereby to exclude this Winding from the talking and impulsing circuits. At RA35I and.RC352 the relay R350 completes a path for applying ground to the control conductor C482, which path extends from ground at RC352 by way of RA35I, C483, RC432 and RA43I to the control conductor noted. When ground is applied to this control conductor, the line 486 is marked as busy in the bank contacts of the numerical switches to which the trunk line 346 extends. At RA356, the relay R350 prepares a circuit, traced hereinafter, for energizing the upper winding the release relay R360 and, at RA351. the relay R350 prepares a holding circuit for R360.

The relay R4I5 operates substantially simultaneously with the operation of R350 and, upon operating, completes, at RA4I9, a circuit for energizing R420, this circuit extending from ground at RA434 by way of RC435, RA4I9 and the Wind-y ing of R420 to battery. At RA4I6 and RC4I1, the relay R4I5 opens a point in its priming circuit, and, at RA4I6 and RC4I8, it prepares a point in one of the holding circuits for R430. When R420 operates, it completes, at RA424, a holding circuit for itself, this circuit extending from ground by way of the resistor 426, RA424, RA4I9 and the winding of R420 to battery: At RA425, the relay R420 opens a point in the circuit, traced hereinafter, for energizing the lower winding of R440 and, at RA42I and RC422, it completes an obvious circuit for energizing the slow-to-release hold relay R430.

When R430 operates, it completes, at RA43I and RC433, an obvious alternative path for applying ground to the control conductor C482 and,

at RA434 and RC435, it interrupts a point in the above-traced operating circuit for R420. At Ram and Rom, the remy R430 compia-.es the above-mentioned holding circuit for itself, this circuit extending by way of RA4l6, RC4I8 and the winding of R430 to battery. At RA431, the relay R430 prepares a circuit, traced hereinafter, for energizing the lower winding of R450. At RA438 and RC439, the relay R430 opens a point in the circuit, traced hereinafter, for energizing the release magnet 412 and, at RA438 and RC438', it prepares a holding circuit, traced hereinafter, for the slow-to-operate relay R440. With the four relays R350, R4l5, R420 and R430 operated, the apparatus in the repeater terminating the line 486 is conditioned to respond to the impulses of the rst or prex digit dialed at the operators telephone in the manual oiilce 480.

The arrangement illustrated in Figs. 3 and 4 is similar to that illustrated in Figs. 1 and 2 in that the dialing of a prefix digit of ten impulses is a prerequisite to the extension of the connection to the non-numerical line switch 400. The purpose of providing this arrangement is the same as that stated previously in the description of the apparatus illustrated in Figs. 1 and 2, namely, to prevent any of the regular automatic switching equipment provided in the automatic exchange from being uselessly tied up when reverting calls are initiated on the line 486. During the dialing of the prex digit, the four relays R4l5, R420, R440 and R450 respond to the impulses thereof and function to repeat corrected impulses to the operating magnet 41| of the switch 410. More particularly, at the beginning of the first impulse of the prex digit, and when the line circuit is opened at the impulsing device provided at the operators telephone station, the line relay R4|5 restores to interrupt, at RAUS, the above-traced holding circuit for R420 and to complete, at RA4I6 and RC4I'1, a priming circuit for itself. The last-mentioned circuit extends from ground at RA434 by way of RA436, RAUS, RC4I1, the resistor 4|1 and the winding of R4|5 to battery. It is pointed out that the resulting energization of R4|5 is insuiiicient to cause the operation of this relay and that such energization is provided for the purpose of rendering this relay more sensitive in its operation when the line circuit is subsequently closed at the end of the open circuit pulse. When R4 I 5 restores, it not only completes its priming circuit, in the manner pointed out above, but interrupts, at RA4I6 and RC4I8, the above-traced holding circuit for R430. Due to its slow-to-release characteristic, however, the last-mentioned relay remains operated during impulsing. When the holding circuit for R420 is interrupted at RA4I9 upon the restoration of R4l5, the relay R420 restores to open, at RA42I and RC422, the operating circuit for R430 and to complete,l at RA42| and RC423, the prepared circuit for energizing the lower winding of R450, this latter circuit extending from ground at RA42I by way of RC423, RA431, RA44I and the lower winding of R450 to battery. Upon operating, the relay R450 completes, at RA453, a path for shortcircuiting its upper winding, thereby to render itself slow-to-release. At RA452, the relay R450 completes an alternative and obvious holding circuit for the hold relay R430. At RA455, the relay R450 completes av circuit for energizing R440, this circuit extending by Way of the resistor 421, the restored armature RA425 and the lower winding of R440 to battery. Since the upper Winding of R440 is normally short-circuited at RA443, this relay is slow to operate. After an interval, however, R440 operates to complete, at RA444, the above-mentioned holding circuit for itself, this circuit extending from ground at RA438 by way of RC438', RA444, the resistor 421, RA425 and the lower winding of R440 to battery. lAt RA44I, the relay R440 interrupts the abovetraced circuit for energizing the lower winding of R450 and, at RA442, it prepares an alternative operating circuit for R420. At the end of the first open circuit pulse, and when the impulsing springs of the impulsing device located at the operators station in the exchange 480 are again closed, the relay R4|5 reoperates to interrupt, at RA4I6 and RC4I1, its priming circuit and to recomplete, at RA4I 6 and RC4I8, the holding circuit for R480. At RA4'I9, the relay R4|5 amasar completes the above-mentioned alternative -operating circuit for R420, this circuit extending from ground at RA442 by way of RA4|9 and the winding of R420 to battery. 'I'he relay R420, upon reoperating, completes, at RA424, its holding circuit as traced above and opens, at RA425, the holding circuit for R440, causing the last-mentioned relay to restore. At RA42| and RC422, the relay R420 recompletes the operating circuit for R430 and, at RA42| and RC423, it interrupts a further point in the above-traced circuit for energizing the lower winding of R450. After an interval following the deenergization of its lower winding, the relay R450 restores to open, at RA455, the above-traced operating circuit for R440 and to interrupt, at RA452, a point in the above-mentioned alternative holding circuit for R430. During each succeeding impulse following the rst, the four relays R4I5, R420, R440, and R450 operate in the sequence ljust described. Since in the present assumed case the preliminary digit dialed at the operators station comprises ten impulses, it will be understood that, during this digit, the cycle of operation of the relays noted is repeated ten times. 'I'he relay R450 is the pulsing relay and it will be apparent from the foregoing description that the relation between the period of deenergization and the period of energization of this relay during each impulse is, within limits, independent of the relation of the corresponding periods for the line relay R4 I 5. More particularly, the operation of R4|5 at the beginning of each impulse cycle initiates the operation of the-three relays R420, R440 and R450 to repeat the impulse, and the extent of the period during which R450 is energized depends primarily upon the slow-to-release characteristic of vthis relay and the slow-to-operate characteristic of R440.

During the period of each impulse when the pulsing relay R450 is operated, a circuit is completed for energizing the operating magnet 41| of the switch 410, this circuit extending fromy ground at RA454 by way of RA463 and the winding of the magnet 41| to battery. Obviously, at the end of the rst and each succeeding impulse, the above-traced circuit for energizing the magnet 41| is opened. Each ltime this magnet is deenergized following its energization, it steps the wiper 415 one step so that, at the end of the preliminary digit, the wiper noted will be left standing in engagement with the tenth contact of the set 414, assuming that the line relay R4|5 is faithfully responsive tothe impulses dialed at the operators station in the distant ofilce 430. When the first step is taken by the wiper 415, theoifnormal springs 413 are closed to prepare-a circuit, traced hereinafter, for energizing the release magnet 412. This circuit is held interrupted at the operated armature RA433 ofthe hold relay R430 for the duration of the call.

If the wiper of the switch 410 is successfully operated into engagement with its associated tenth contact in response to the dialing of the preliminary or prefix digit at the operators station, an obvious circuit is completed for energizing R460 immediately the wiper 415 is moved into engagement with the tenth contact of the set 414. Upon operating, the relay R460 interrupts, at RA463, a point in the above-traced circuit for energizing the operating magnet 41|, thereby to prevent further actuation of the impulslng device at the'operators station from causing further operation of the switch 410. At RA463', the relay R460 completes a'multiple path including the two conductors C433 and C433 for short-circuiting the upper winding of R350. At its armatures RA46I and RA462, the relay R460 completes a loop circuit to the non-numerical line switch 400 and including the trunk line 346. More particularly, this loop circuit extends from one terminal of the line relay conventionally provided in the switch 400 by way of RA462, C485, the repeater winding 3|8, RA32| and its associated upper contact, the resistor 3|2, the repeater winding 3|3, C484, RA45| and RA46| to the opposite terminal of the line relay embodied in the line switch'400. In response to the completion of this loop circuit, the line switch 400 operates to select a trunk leading to an idle selector switch. If it be assumed, for example, that the switch 405 is the first available idle selector switch, the line switch 400, upon seizing the trunk extending to this selector switch,

operates to extend the loop circuit' thereto, whereupon this selector switch is conditioned to respond to the impulses of the second digit dialed at the operators station.

During the impulses of this second digit, the four relays R4I5, R420, R440 and R450 respond, in the exact manner pointed out above. Each time the relay R450 operates, it interrupts, at RA45I, the above-traced loop circuit which is now extended to the selector switch 405. Thus, the

impulses dialed at the operators station are ey peated to the selector switch noted and this selector switch responds thereto by selecting the group of connector switches having access to the called line 30| and including the switch 4|0. Shortly following the conclusion of the second digit, the selector switch 405 automatically operates to select a trunk leading to an idle connector.

switch in the selected group. If it be assumed, for example, that the switch 4|0 is the iirst available idle switch of the selected group, when the trunk leading to this connector switch is seized, the loop circuit is extended thereto and the switch is conditioned to respond to the impulses of the third and fourth digits dialed at the operators station. The connector switch 4|0 operates in a conventional manner to select the called line 30| in response to the final two digits, to test the condition of the line, to return busy tone over the established loop to the operator in the distant manual omce in the event the line is found busy, and to project ringing current over the called line 30| in the event the line is idle. 'I'he desired talking connection is completed between the calling and called substations when the call is answered at the substation E. The operator at the oflice 400 retains her answer plug in the jack terminating the line 486 during the vinterval when the line is occupied with the call.

In the illustrated arrangement, no provision is made for -giving the manual office operator a disconnect signal. It will be understood, however, that a relay, corresponding to R|60 illustrated in Fig. l of the drawings, may be included in the repeater for performing this function. In such case, the winding of the relay corresponding to RI 60 would be substituted for the resistor 3|2 and this relay would be provided with an armature for short-circuiting a resistance element provided in the series circuit over which R4|5 and the upper winding of R450 are energized. In any case, the release of the connection as established in the manner just described is entirely under the control of the operator'in the manual omce 430 who,

upon ascertaining that the conversation is com-A pleted, may initiate the release of the operated apparatus by withdrawing the answer plug from the jack terminating the line 486. When this is done, ground is removed from the line conductor 436 to interrupt the circuit over which R416 is being held energized. Upon restoring, the relay R4| 5 interrupts, at RA4I9, the holding circuit for R420, causing the last-mentioned relay to restore to interrupt, at RA42I and RC422, the operating circuit for R430 and to complete, at RA42| and RC423, the operating circuit for R450.l When R450 operates, it completes, at RA455, the circuit for energizing the lower winding of R440 and, at RA452, the above-traced holding circuit for R430. When R440 operates, it interrupts, at RA44I, the operating Vcircuit for R450, causing the last-mentioned relay to restore after an interval to open, at RA452, the remaining holding circuit for R430 and, at RA455, the operating circuit for R440. When, shortly thereafter, R430 restores, it interrupts, at RA438 and RC438, the completed holding circuit for R`440, causing the last-named relay to restore. At RA431, the relay R430 interrupts a further point in the operating circuit for R450. At RA43| and RC433, the relay R433` momentarily removes ground from the control conductor C482, but ground is restored to this conductor upon the complete restoration of RA43 i, this second ground extending from RC352 to C482 over a path traced previously. At RA438 and RC439, the hold relay R430, upon restoring, completes a circuit extending by way of the oil-normal springs 413 for energizing the release magnet 412. When the release magnet 412 is energized, it causes the Wiper 415 to be restored to its home position, at which time the ofi-normal springs 413 are opened to interrupt the circuit for energizing the release magnet 412. The wiper 415, upon leaving its associated tenth contact, opens the operating circuit for R460, causing this relay to restore to interrupt the loop circuit extending to the operated switch train comprising the switches 400, 405 and 4i0. Thus, the automatic switches are caused to restore in a manner which will be apparent from the preceding description.

The arrangement of the apparatus is such that the line busying ground may not be removed from the control conductor C482 immediately an established connection is cleared out. Thus, it is pointed out above that the relay R350 functions to hold ground on C482 so long as it remains operated. Following its operation, this relay is entirely under the control of R360 which latter relay is, in turn, arranged to be controlled by the pulse generator 385. More particularly, when the first ground pulse is applied to C303 by the pulse generator 385, following the operation of R350, the upper winding of R360 is energized over a circuit extending by way of RA356. Upon operating, the relay R360 completes a holding circuit for itself, this circuit extending from ground at RA351-by Way of RA36| and the lower winding of R360 to battery. At RA362, the relay R360 prepares a path for short` circuiting the lower winding of R350 when a. ground pulse is subsequently impressed on the second pulse lead If the established connection is released in the manner described above before this lastmentioned ground pulse is applied to C304 the relay R350 remains energized by Way of its holding circuit to retain busying ground potential on the control conductor C482. On the other hand, if the duration of the call is such that a ground pulse is applied to C304 before the connection is cleared out the relay R350 is caused to restore and busying ground potential is removed from the control conductor C482 immediately the connection is cleared out; In either case when the second ground pulse is applied to C364, the

lower winding of R363 is short-circuited over a path extending by way of C334, RA362 and the lower winding noted to ground at RA356. When this occurs, the relay R360 restores. If, at the time R366 restores, conversation is still being held over the established connection, the upper winding f R360 is short-circuited at the operated armature RA463' of the relay R460. Hence, R360 cannot reoperate since the first operation in the release of the connection is the interruption of the circuit for energizing the upper or operating winding of this relay. Similarly, if the lower`winding of R360 is short-circuited after the connection is cleared out, this relay cannot reoperate since its operating circuit is open under these circumstances. When R360 restores after the connection is cleared out, lit removes, at RA35I and RC362, ground potential from C462. At RA36I and RC353, the relay R360 applies battery potential to this conductor over the path traced above, thus marking the line 466 as idle. At RA355, the relay R350 opens a point in its holding circuit and, at RA36'I, it interrupts the holding circuit for R360 causing the last-mentioned relay to restore. Thus, the apparatus is entirely released and the line 483 is marked as idle in the bank contacts of the connector switches to which the trunk line 346 extends.

The manner in which the apparatus illustrated in Figs. 3 and 4 operates when a call intended for one of the automatic subscribers substations, such, for example, as the substation E, is initiated at one of the substations associated with the line 486 and equipped for automatic service, is identical with that just described. In this case, however, and as was pointed out above, the intervention of the operator in the manual oiilce 480 is not required since the necessary impulsing may be performed'at the calling substation by the calling party.

With the arrangement illustrated in Figs. 3 and 4, it is contemplated that all reverting calls initiated at the substations associated with the line 486 will be completed directly, or without the assistance of the operator in the manual office 480, means including the relays R350 and R360 and the pulse generator 336 being provided for marking the line as busy in the numerical switches having access thereto during the periods when this line is occupied with calls of a reverting nature. Such calls may, of course, be forwarded to the desired substations through the intervention of the operator in the oiiice 480 in a manner substantially similar to that described previously with reference to the arrangement illustrated in Figs. 1 and 2. In either case, when the calling party actuates the magneto generator at the calling substation to project ringing current over the line 466, the upper winding of R350 is energized in the manner described above. Upon operating, the relay R350 performs the functions enumerated previously; that is, it short-circuits its upper winding, completes its holding circuit, and, at RA35| and RC352, applies ground to the control conductor C482. The relay R4l5 may or may not be caused to operate, depending upon the character of the substations to be used in the reverting call connection. If one of these substations is equipped for full automatic service, or if the operator in the manual oiilce is called upon to assist in completing the connection, a direct current circuit similar to that traced above will be completed for energizing R4i5. If R4I5 is caused to operate, it initiates the sequential operation oi' R420 and R430 in the manner pointed outpreviously. When R430 operates, it completes, at RA48I, the above-noted alternative circuit for applying ground to C482 and prepares, at RA431, the operating circuit for R450. Since, in this case, no dialing is required in completing the reverting call connection, no further operations occur in the apparatus illustrated until the connection is released. During the interval when the line 486 is occupied with the call. however, and if the mode of completing the connection results in the energization of the three relays R4I5, R420 andI R430, the line is guarded against seizure by any one of the numerical switches having access thereto through the application to ground to` C482 occasioned by the continued energization of the hold relay R430.

If, on the other hand, thek connection is established between two substations equipped for manual service only and without the assistance of the operator in the manual omce, such that the relay R350 is alone energized, this relay functions to maintain busying ground on the control conductor C482. In this case busying `ground is maintained on C482 for a predetermined time interval which is independent of the actual idle or busy condition of the line. More particularly, if the reverting call connection is cleared out before the pulse generator 385 and the relay R360 operate to'cause the restoration of R350 in the manner set forth above, the last-mentioned re lay is held energized over its holding circuit to maintain the line 486 marked as busy even though the line is actually idle. Conversely, if the connectionis not cleared out at the calling and called substations until after the second ground pulse is applied to C304, followingthe operation of R350, this relay restores to remove, at RA35I and RC352, busying ground potential from C482 even though the line is still busy. Moreover, no circuit is available for causing the reoperation of R350, since in this case, no direct current circuit is established by Way of the lin 486 for energizing the relay R4I5.

In the case where one of the substations involved in the reverting call connection is equipped for automatic service or where the operator in the manual oiiceintervenes in setting up the connection and remains plugged in on the connection until the conversation is terminated, the relay R350, in cooperation with the pulse generator 385 and the relay R360; functions to test the condition of the line at spaced intervals and to remove the busy marking when a test indicates that the line is idle. In this case the three relays R4l5, R420 and R430 are held energized for the duration of the call and the ,last-mentioned relay maintains busying ground onv the control conductor C482. Assuming the connection is maintained for a considerable time interval, the pulse generator 385, in combination with R360-, operates to cause the partial restoration of R350, in the manner described previously, after a given time interval. Upon partially restoring, R350 interrupts, at RA354, the path short-circuiting its upper winding, causing this winding to be energized in series withthe winding of R4l5. Thus, R3I5 reoperates to recomplete its holding circuit and to reprepare, at RA356, the circuit for energizing the upper winding of R360 when a succeeding ground pulse is applied to C303. It will be apparent that so long as the connection is maintained the cycle of operations just describedv is repeated at spaced intervals. When the connection is ultimately cleared out ground is removed from. the line conductor 486 and the relay R4I5 is caused to restore in the manner pointed out above. 'Ihe restoration of l'R4I5 is followed by the restoration of R420, which latter relay, upon restoring, completes, at RA42I and RC423, the above-traced operating circuit for R450. The relay R450, upon operating, completes, at RA454, the above-traced circuit for energizing the magnet 41| and, at RA455, the previously traced operatingcircuit for R440. Thereafter and when R450 restores following the operation of R440, the wiper 415 ofthe switch 410 is operated one step oif normal to close the olif-normal springs 413. When R450 restores, it also opens the only remaning holding circuit for R430, causing the last-mentioned relay to restore, after an interval, to complete, at RA438 and RC439, the abovetraced circuit for energizing the release magnet 412. When the release magnet is energized the switch 410 is restored to normal and the oir-normal springs 413 are opened to interrupt thecircuit for energizing the release magnet. When R430 restores, it interrupts, at RA438 and RC438', the holding circuit for R440, causing the lastmentioned relay to restore. At RA43I, the relay R430 disconnects the control conductor C482 from. ground at RC433 and connects it to ground at RC352. When thereafter the relay R850 is caused to restore in the manner described above, no circuit is available for energizing the upper winding thereof and hence this relayiremains in its restored position. Upon restoring, yfollowing the restoration of R430, the relay R350 disconnects the control conductor C482 from ground at RA35I and RC352 and completes the abovetraced path for applying battery potential thereto. Thus, the line is marked as idle and the apparatus embodied in the repeater terminating the line is restored to normal.

While there have been described what are at present .considered to be the preferred embodiments of the invention, it will be understood that various modifications may be made therein, and it is intended in Vthe appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

We claim:

v1. In a telephone system, a telephone'station, a ringing current generator at said station, an automatic exchange, a line extending between said station and said exchange, a plurality of substations associated with said line, a plurality of additional lines extending to said exchange, automatic switching equipment in said exchange for setting up connections between said additional lines and between said first-named line and said additional lines, and control apparatus associated with said first-named line; said apparatus being so connected and arranged that a call to one of said substations initiated on one of said additional lines and extended through a portion of said automatic switching equipment is routed over said first-named line to said station and said one substation is thereafter signaled by projecting ringing current from said generator back over said first-named line to said one substation, a call to one of said substations .initiated at another of said substations is routed Yover said first-named line to said station and said one substation is signaled by projecting ringing current from said generator back over said first-named line to said one substation, and a call to one of said additional lines initiated at one of said substations is routed over said rst-named line t0 said station and is then routed from4 said station back over said first-named line and through a portionof said automatic switching equipment to said one additional line.`

. 2. In a telephone system, a telephone station, a ringing current generator at said station, an automatic exchange, a line extending between said station and said exchange, a substation associated with said line. a plurality otadditional lines extending to `said exchange, automatic switching equipment in said exchange for setting up connections between said additional lines and between said first-named line and said addition- Aal lines, and control'apparatus associated vwith` said rst-named line, said apparatus being so connected and arranged that a call to said substation initiated on one of said additional lines andextended through aportion of said automatic switching equipment is routed over said first-named line to said station and said substation is thereafter signaled by projecting ringing current from said generator back over said ilrstnamed line to said substation, and a call to one of said additional lines initiated at said substation is routed over said rst-named line to said station and is then routed from said station back over said rst-named line and through a portion of said automatic switching equipment to said one additional line.

3. In a telephone system, a telephone station, a ringing current generator at said station, an automatic exchange, a line extending between said station and said exchange, a plurality of substations associated with said line, a plurality of additional lines extending to said exchange, automatic switching equipment in said exchange for setting up connections between said additional lines and between said iirst-named line and said additional lines, and control apparatus associated with said rst-named line; said apparatus being so connected and arranged that a call to one of said substations initiated at another of said substations is routed over said rstnamed line to said station and said one substation is signaled by projecting ringing current from said generator back over said first-named line to said one substation, and a call to one of said additional lines initiated at one of said substations is routed over said first-named line to said station and isl then routed from said station back over said ilrst-named line and through a portion of said automatic switching equipment to said one additional line.

4. In a telephone system, a telephone station, a ringing currentgenerator at said station, an automatic exchange, a line extending between said exchange and said station, a plurality of substations associated with said line, a plurality of additional lines extending to said exchange, automatic switching equipment in said exchange for setting up connections between said additional lines and between said first-named line and said additional lines, and control apparatus associated with said first-named line; said apparatus being so connected and arranged that a call to one of said substations initiated on one of said additional lines and extended through a portio of said automatic switching equipment is routed over said iirst-named line to said station and said one substation is thereafter signaled by projecting ringing current from said generator back over said first-named line to said one substation, and a call to one of said substations initiated at another of said substations is routed over said rst-named line to said station and said one substation is then signaled by projecting ringing current from said generator back over said ilrst-named line to said one substation.

5. In a telephone system, a telephone station, a ringing current generator at said station, an automatic exchange, a line extending between said station and'said exchange, a substation associated with said line, a plurality of additional lines extending to said exchange, automatic switching equipment in said exchange' for setting up connections between said additional lines and between said first-named line and said additional lines, and control apparatus associated with said first-named line; said apparatus being so connected and arranged that a call to said substation initiated on one of said additional lines and extended through a portion of said automatic switching equipment is routed over said ilrstnamed line to said station and said substation is thereafter signaled by projecting ringing current from said generator back over said iirst-named line to said substation.

6. In a telephone system. a telephone station, a ringing current generator at said station, an automatic exchange, a line extending between said station and said exchange, a plurality of substations associated with said line, a plurality of additional lines extending to said exchange, automatic switching equipment in said exchange for setting up connections between said additional lines and between said tlrst-named line and said additional lines, and control apparatus associated with said iirst-named line; said apparatus being so connected and arranged that a call to one of said additional lines initiated at one of said substations is routed over said rst-named, line to said station and is then routed from said station back` over said rst-named line and through a portion 0I said automatic switching equipment to said one additional line.

7. In a telephone system, a manual oflice, an operators telephone station in said ofiice, a ringing current generator at said station, an automatic exchange, a trunk line of the ground return type extending between said automatic exchange and said station, a plurality of substa tions associated withvsaid line and each including telephone substation equipment connected between ground and the ungrounded side of said line, a plurality oi additional lines extending to said automatic exchange, automatic switching equipment in said automatic exchange for setting up connections between said additional lines and between said iirst-named line and said additiona1 lines, and control apparatus associated with said first-named line; said apparatus being so connected and arranged that a call to one of said substations initiatedy on one or said additional lines and extended through a portion of said automatic switching equipment is routed over said first-named line to said station and said one substation is thereafter signaled by projecting ringing current from said generator back over said first-named 'line 'to said one substation, a call to one of said substations initiated at another of said substations is routed over said iirst-named line to said station and said one substation is signaled byiprojecting ringing current from said generator back over said first-named line to said one substation, and a call to on'e o! said additional lines initiated at one of said substations is routed over saidiirst-named line to said station and is then routed from said station back over said rst-named line and through a portion of said automatic switching equipment to said one additional line. 

